I found you forum after receiving a $ 549 electric bill.  I have reviewed old posts for the last week and appreciate
all the great info on the forum.  I have applied members ideas and comments to try to explain our Geo costs.
I have come to the conclusion that I think we have a Geo success story.  I also have some technical questions
to make sure we are efficient as possible.

Early in my Geo education I was told that long runs are most efficient using the Geo, and to only use the aux. heat
strip if the Geo cannot maintain the setpoint.  I have the heat strip on its own 80 amp breaker that has been turned
off for the past 2 winters. I have only turned it on to make sure it works.  One time last winter we had a outside
temp of  14 below F, and our interior dropped as low as 63 degrees, with a 64 Degree F setpoint.  We hold the winter
temp. at 64 degrees F and 75 degrees F in summer.

Our FHP Geo unit has operated flawlessly for 2.5 years, with only filter changes, and checking it over. We always
have enough hot water, except for 2 times last spring.  The Desuperheater pump is always switched on.

I have 3 Questions:

Return Air Ducting.  Geo Unit has 28" Wide x  30" High opening (840 sq. In.) 2-16"x30" filters recommended by FHP manual.
As-Built:     Blocking Plate installed to allow 1-14"x 25" & 1-16"x 25" air filters (635 sq. In.)
                  Metal plenum 31" H x 28" x 20" D, not insulated (560 sq. In. top dimensions)
                  Owings Corning QuietR Duct Board I.D. Connecting to plenum is 15"x25.5" (383 sq. In.)
I am concerned about the smooth flow of return, is it important?  The house has even temps. throughout.

In our other previous homes with gas furnaces, a lower setpoint saved money.  Is this always true with Geothermal
also?

In reading the forum I am concerned that our Geo unit was run without return ducts during plastering. I have
checked the coils behind the filters and they are coated in white chalky dust.  What is the recommended way of
cleaning plaster dust from the 3 row coils?

Background:

House Design:  3,500 sf 1-1/2 story, 3,100 sf main floor, 400 sf open loft, 9' ceilings, True SW exposure,
R-38 ceilings, R-21 walls, Stucco cement exterior, 94 Pella windows, Hardwood & Tile floors. Basement: 3,100 sf,
insulated, unheated, unfinished. House has large thermal mass and does not change temp. quickly.  Interior warms
quickly when sun is higher in Feb. & Mar. afternoons.  Built during 2007-2008.

Design Data:

1) Stanton, Michigan, 48888 Zip

2) Heating Load:  86,900 btu/hr
    Cooling Load:  64,700 btu/hr
    Internal Gains: 15,000 btu/hr

3) Florida Heat Pump, GT070 (6ton) w/HR0003-1 Desuperheater, 2 Marathon 50 Gal. Elec. hot water heaters (1 Storage
only, 1 top element set at 110 F), 15kw aux. heat strip.

4) Closed loop, 3-290' trenches (870' total), 4 ft wide, 10' deep.  5,220' of 3/4" HDPE pipe, 6 pipe design
   on 2' centers, buried at 10' & 8' in dry compacted sand.  Flow Controller 3 model AFCG2B2, with 2 Grunfos 116
   pumps and brass valve.  70' of 1-1/4" HDPE from manifolds to loop controller.

5) $ 0.1163 per kwh including taxes.  Usage 4,722 kwh total from 12/15/10 to 1/17/11 (34 days) ($ 549.52).  Our
   lowest Geothermal use months are May & Oct, with approx. 1,300 kwh avg. per month.

6 & 7)  Outside Conditions: 2/10/11 @ 12:00 P.M.  11 degrees F. With 11 mph winds, sunny.
           White Rogers 1F95-1271 setting:  64 degrees hold, heat, Stage 1
           Previous 24 hours: High: 16 degrees F. Low:  8 degrees below zero F. Overnight.
           Geo had been running for approx. 7 hours straight on Stage 1 & 2 until approx. 10:00 A.M.

           EWT: 37 degrees F.
           LWT: 33 degrees F.
           EAT:  61 degrees F.
           LAT:  84 degrees F.

           Outside Conditions: 2/11/11 @ 12:20 P.M.  19 degrees F. With 21 mph winds, mostly cloudy.
           White Rogers 1F95-1271 setting:  64 degrees hold, heat, Stage 1
           Previous 24 hours: High: 17 degrees F. Low:  9 degrees F. Overnight.
           Geo running for 17 Min. on Stage 1, off for 13 Min. for the next 3 hours.

           EWT: 41 degrees F.
           LWT: 34 degrees F.
           EAT:  62 degrees F.
           LAT:  85 degrees F.

8)  Percent of load to be covered by Geo:  Unknown.  Max. System Balance Point: 19 degrees F.
                                                                                     Min. System Balance Point: 11 degrees F.

9) No running assessment ever made.  Contractor out of business about the time we moved in 12/08.

10) Projected Costs in 2011 rates:              Actual Use:    Total use for 2010:    $ 3,160.33

    Heating:        $ 1,491.00                                               Est. normal use per    $    139.56
    Cooling:        $    142.00                                               month
    Hot Water     $    373.00                                               Normal use per year   $ 1,674.72
    Total             $ 2,006.00            
                                                                            Est. Heating,Cooling,DHW        $ 1,485.61    

2007 System Design Data for our home:

Loop Temp.:  Min. 27 degrees F and Max.. 105 degrees F.
Heating Setpoint:  70 degrees F.
Cooling Setpoint:  75 degrees F.
Heating Temp Diff:  70 degrees F.
Cooling Temp.Diff.  20 degrees F.
Aux. Heat required: 13kw
Max.. Loop Extreme:  80.9 degrees F.
Min. Loop Extreme:   30.6 degrees F.

Thank you
   

1) I don't like the idea of restricting the return. I also don't like using 2 filters if it can be avoided - the gap between them is a potential dust bypass. Filters Now and Filters Direct both sell Accumulaire brand filters in a wide range of sizes - I just checked and 28x30x2 is an option. The installer may have been lazy or ill-informed, or cake up with a creative way to keep you from having to buy pricey filters from FHP.

2) Operation that ingested plaster dust is unfortunate. It may be possible to cobble together PVC fittings and shop-vac attachments and a SOFT brush so as to clean the coil using the filter slot without disassembly. Condensate from summer cooling may have turned the dust into mud and bonded it to the coil. That would make cleaning much harder. Fins in air coil are VERY thin and easily bent, once bent they lose heat transfer capability. It may be best to leave well enough alone if the dust isn't too thick.

3) Reduced temperature setpoints save some money - only you can decide if the sacrifice of comfort is worthwhile. Avoid at all costs setbacks if aux strips kick in during recovery - that burns any savings and then some.

Water and air temps look reasonable.

Having tried to clean my last system (that died) I can confirm that the fins are very easily bent.  I had some success using an air compressor and blowing the debris from inside the unit towards the filter, but you have to be very careful not to touch the fins. They make fin combs to straighten them out, but it an art to use it.

Ahh Montcalm County....seems like you step in a lake everytime you turn around. Ice fishermen have to love this weather.
I agree with others. Be very careful when cleaning coil. Fin combs are an art that I have not mastered in more than 20 years of this stuff.
They make a coil cleaner that you can employ in the summer when you run the ac. You spray the foam on and condensation rinses it off.

Good Luck,
Joe

Curt, I found the filters on the web sites you suggested. I will decide if I want to go with a permanent
28"  x  30" filter, or buy a stack of throw always.  I will change the filter rails when I remove the plenum
to clean the coil, after the weather warms up.

Curt, TechGromit, Joe,  In my initial observations with a telescopic mirror and flashlight, the coil looks to be
heavily caked with plaster dust on the intake side.  I have some long, soft haired brushes, plastic dental picks,
shop vac, compressor with regulator set to 30 or 40 psi, automotive fin comb, and a lot of time on my hands. It
looks like a long tedious job, but from what I can see, it needs to be done. I will remove the service cover and
see what the coil looks like from the inside.  I wish I would have been smart enough to address the plaster dust
earlier. I will search for the coil foam.

Joe,  I see you know the area.  Did you know there is a glacier in Montcalm County, I know because I built my house
on it.  I know this because sometimes my outside thermometer is way colder than the weather report on TV and radio.

Curt, TechGromit, Joe,  I want to thank you guys for all your insight and helping us novices understand our
Geothermal systems.  

Best Regards, Kustom

I thought Michigan glaciers summered in the UP!
Really uncomfortable with your suggestion of the dental pick. Be very careful.
j

Looks like a greatly running system......

Posted By Kustom1911 on 17 Feb 2011 01:27 PM
Curt, I found the filters on the web sites you suggested. I will decide if I want to go with a permanent
28"  x  30" filter, or buy a stack of throw always.  I will change the filter rails when I remove the plenum
to clean the coil, after the weather warms up.

I use 4 inch thick air filters and replace them every three months, I write the date on the filter when replacing them.  If you compare a 3 month old filter with a new filter, you'll notice it's off white, compared to new white filter. This is what you want, filters that are any dirtier than that are becoming clogged and actually start to pull the dust through the filter to get trapped on the exchanger. If your only using 1 inch thick filters, I would replace them monthly. The single greatest failure of any HVAC system is the homeowners failure to replace the systems air filters on a regular basis.  My former system had electronic filters, they work, but they still require you to clean the grills every few months, they are not maintenance free. I prefer filters, this way I don't have to wonder if the units electronic filter is still working.  The electronic grill filters need to be placed in a dishwasher to be property cleaned, its a real project. Being lazy, I rather just toss in a new filter, in quantity, they run about $20 each from an online supplier. I generally get 8 at a time to get free shipping from the vendor.  
  

3 months may be needlessly frequent for 4" deep filters. I wouldn't judge a filter by its color. A far better way is to measure delta-P across it and change it only when indicated by excess delta-P

There are analog instruments (Magnehelic) out there for well below $100 as well as digital devices for <$200. That's not money I'd spend in lieu of changing $3 throwaways, but at $20 per pop, I want the filter to be there as long as indicated by delta-P. A rise of 0.05 - 0.10 in. WC is a reasonable change interval.

It is also worth ensuring the filter fits tightly or else dust simply bypasses it. A bit of soft self adheasive pipe insulation tape or door weatherstripping works well.